The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
During the combustion process of an internal combustion engine (ICE), gasoline is oxidized and hydrogen (H) and carbon (C) combine with air to produce various chemical compounds. The chemical compounds may include, for example, carbon dioxide (CO2), water (H2O), carbon monoxide (CO), nitrogen oxides (NOX), unburned hydrocarbons (HC), and sulfur oxides (SOX).
Exhaust systems of an ICE may include a catalytic converter, a primary oxygen sensor and a secondary oxygen sensor. The catalytic converter reduces exhaust emissions by chemically converting an exhaust gas into carbon dioxide (CO2), nitrogen (N), and water (H2O). The primary and secondary oxygen sensors are used to detect oxygen content of the exhaust gas. The primary oxygen sensor monitors the oxygen level associated with exhaust gas entering the catalytic converter. The secondary oxygen sensor detects the oxygen level associated with exhaust gas exiting the catalytic converter. The primary and secondary oxygen sensors provide feedback signals that are used to maintain an air-to-fuel (A/F) ratio of the ICE at a chemically correct or stoichiometric A/F ratio to support catalytic conversion processes.
Exhaust diagnostic systems may monitor the catalytic converter and the primary and secondary oxygen sensors to ensure proper operation of engine and exhaust systems. Traditionally, passive tests and/or intrusive tests are implemented to check the operation of the primary and secondary oxygen sensors. During the intrusive tests, A/F ratios are intrusively adjusted and response of the primary and secondary sensors is monitored. Although the intrusive tests allow for error detection of the primary and secondary oxygen sensors, the intrusive tests can increase exhaust emissions and/or cause engine instability and reduce driveability.